This invention relates generally to the field of float valves--valves which control the flow of water through a system in response to the movement of a float device in a reservoir of water with changing surface level. More particularly, the invention relates to such valves which are composed of a plastic or polymeric material.
Float valves are well known devices used to control water flow and are commonly used to refill water tanks to a desired level when water in the tank has been removed. Typical devices which contain float valves are toilets, water storage tanks, water aerator tanks, etc. The vast majority of such valves, because water flows through the device and because they are often found in wet environments, are made of metal--most commonly brass or stainless steel. A problem with the brass metal valves is that they easily corrode and trap mineral deposits, which means that the valves must be replaced on a regular basis. The stainless steel valves are less subject to corrosion and depositing, but are relatively high in cost. Plastic valves offer a solution to the problems of corrosion and deposit while maintaining a relatively low cost of manufacture, but suffer from several problems in the embodiments currently known in that the force applying components are subject to failure, the plastic valves are suitable only for low volume flow rates because of size limitations to the inlet orifice and the use of O-rings to seal the gap between the piston and the housing. The O-rings make movement of the piston difficult and the valve is very susceptible to jamming. The O-rings are also relatively easily unseated in high pressure applications. Even with the small inlet orifice size, the plastic valves heretofore known do not seal well after repeated uses. Another problem encountered in both metal and plastic valves is that the tip washer, which is shaped as a truncated cone and seats against the inlet orifice of the valve to seal off the inlet conduit, is mounted within a recess formed by an annular collar or rim on the end of the piston. The presence of this collar or rim blocks or limits water flow around the tip washer, producing a reduced flow rate.
It is an object of this invention to provide a float valve constructed of plastic which is relatively low in cost, does not readily corrode, does not allow excessive mineral deposits to build up on the internal surfaces, does not easily jam, is strong, is able to handle large volume flow rates, operates smoothly and easily, and retains the ability to totally seal the flow conduit over long term use.